Recently, there has been an increasing demand for an improvement of performance and more versatile applications of construction machines, and more advanced electronic control of a construction machine has been developed to cope with the demand. In such a situation, an electronic control system used for that purpose is required to execute high-speed processing and to employ a highly intelligent microcomputer as an essential. As a result, problems arise in that the production cost is increased and control units and wire harness are complicated with an increased number of input/output signals of the system.
With the view of overcoming those problems, it is proposed to distribute a controller for performing overall control of a construction machine by dividing control functions required in a construction machine, i.e., a control target, in units of function, providing a controller (control unit) for each of the divided function units, and connecting the control units to each other via a network. For example, JP,B 8-28911 discloses an electronic control system for a construction machine, in which a control unit, such as an engine control unit or a pump control unit, is provided for each piece of equipment and these control units are interconnected by a single multi-transmission serial communication circuit to constitute a network for two-way communication, and hence in which a system extension can easily be realized.